Method of making vacuum components

ABSTRACT

A method of making evacuated enclosures such as envelopes for vacuum switches, relays, or interrupters. The method may include a step of brazing the envelope to provide an hermetic seal in a reducing atmosphere at atmospheric pressure. The envelope is then reheated in a vacuum chamber. At least one portion of the envelope is made of a material through which the reducing gas can pass.

United States Patent Lewis B. Steward;

Wesley N. Lindsay, San Jose, Calif. 837,155

June 27, 1969 Apr. 27, 1971 International Telephone and TelegraphCorporation New York, NY.

lnventors Appl. No. Filed Patented Assignee METHOD OF MAKING VACUUMCOMPONENTS 9 Claims, 9 Drawing Figs.

[1.5. 9 29/497, 316/18, 316/19, 316/21 Int. Cl B231: 31/02,

823k 35/38 Field of Search 29/494,

References Cited UNITED STATES PATENTS 1/1927 Smith 2,438,721 3/1948Spencer 29/494X 2,654,822 10/1953 Agule 29/494X 2,747,269 5/ 1956Atchison 29/494X 2,770,033 1 l/ 1956 Zarth 29/494X 2,987,813 6/ 1961Pope et a1. 29/497X 3,241,230 3/ 1966 Batista et al. 29/494 PrimaryExaminer-John F. Campbell Assistant Examiner-R. J. Shore Attorneys-C.Cornell Remsen, Jr., Walter J. Baum, Paul W. Hemminger, Percy P. Lantzyand Thomas E. Kristofferson through which the reducing gas can pass.

- 1 METHOD or Mur ne VACUUM comosnm's BACKGROUND or rr'ira INVENTIONThis invention relates to evacuated enclosures and, more particularly,to an improved method of withdrawing a gas from the interior of anenvelope.

Although the method of the present invention will have a large scope ofapplication and should thus not be limited to the specific uses setforth herein; the invention has been found to possess exceptionalutility in making vacuum switches,

vacuum relays, and vacuum interrupters.

In the past, it has been thepractice to outgas an envelope by heating itin a vacuum chamber. That is, the envelope is heated, and the gasses.therein and therearound are pumped out at the same time. When thedesired vacuum-level is reached, the envelope is sealed by brazing orotherwise.

Due to the fact that the envelope must be heated while it is inside thevacuum chamber, induction heaters must often be SUMMARY OF THE INVENTIONIn accordance with the method of the invention, the abovedescribed andother disadvantages of the prior art are overcome by withdrawing gasfrom inside an envelope after the envelope has been hermetically sealed.In this case, the envelope is provided with at least a portion throughwhich the gas will penetrate.

In accordance with one feature of the invention, the envelope is brazed(hermetically sealed) in a reducing atmosphere at atmospheric pressure.The reducing atmosphere keeps the component parts clean. Further,conventional resistance heaters may also be economically used forheating a large number of envelopes simultaneously at the convenientpressure of 1 atmosphere. The same large numberof envelopes may then beeconomically heated by resistance .heaters and evacuated in a vacuumoven. Moreover, the said large number all maybe heated and evacuated atthe same time. Thus, by processing the envelopes more or less inbatches, production is increased and costs are lowered.

The above-described and other advantages of the invention will be betterunderstood from the'following description when considered in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to beregarded as merely illustrative:

FIG. 1 is a side elevational view showing in actual size a relay uponwhich the present invention may be practiced, the relay including both aswitch portion and an actuating assembly;

FIG. 2 is an enlarged longitudinal sectional view, partly in elevation,through the central axis of the switch portion of the relayillustratedin FIG. 1, the plane'of the section being indicated by line2-2 in FIG. 3;

F IG; 3 is a transverse sectional view taken along line 3-3 of theswitch portion of FIG. 2; i

FIG. 4 is a top plan view of one of the fixed contact assemblies shownapart from the remainder of the switch structure;

FIG. 5 is a longitudinal sectional view,- partly in elevation, throughthe central axis of the actuating assembly of the relay illustrated inFIG. 1;

FIG. 6 is a perspective view of the coil, armature, and resilientbracket employed in the actuating assembly illustrated in FIG. 5; i

FIG. 7 is an enlarged fragmentary vertical section taken FIG. 8 is a topplan view, on a reduced scale, of a sheet metal blank which is bentintothe form of. a bracket utilized. for mounting the armature in theactuating assembly;

FIG.' 9 i s an'exploded view showing in' plan the end of a resilientbracket and the free end of the armature to which the end of the bracketis connected; and

FIG. 10 is a sectional view taken along line 10-10 in FIG. 9 showing inelevation the free end of the resilient bracket.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings,'in FIG. I,there is illustrated a relay 20 upon which the present invention may bepracticed. Relay 20 includes an upper switch portion 22 and a loweractuating assembly 24. As best seen in FIG..2, the switch portion 22 ofthe relay includes an envelope 25 composed of two axially aligned,elongated tubular insulator envelope sections 26 and 28, preferablyformed of ceramic. A third ceramic tubular section 30 is provided forconnecting the switch envelope to the actuating assembly 24. The ceramicsections 26 and 28 are provided at .their remote ends with metallizededges 32 and 34 while the ceramic section 30 has its upper endmetallized as indicated at 36 and its lower outer periphery metallizedas indicated at 37. A first annular metallic terminal electrode 38 ishermetically brazed to the metallized edge 32 of the ceramic section 26while a second annular metallic terminal electrode 40 is hermeticallybrazed to the lower metallized edge 34 of the ceramic section 26. Themetallized upper edge 32 of ceramic section 28 is brazed to the lowersurface of the terminal electrode 40.

A metallic end cap 42 is brazed to the upper surface of the terminalelectrode 38 and closes the upper end of the switch envelope. Preferablythe end cap '42 is provided with an upwardly extending, domed portion44. It is to be noted that this end cap assembly eliminates an appendagewhich constitutes a tubulation employed in prior art relays, thusreducing the cost and complexities of production. End cap 42 ispreferably made of nickel or nickel-iron according to the method of thepresent invention. However, in accordance with the invention,

, nickel may be used by itself.

construction of the armature;

Nickel is used because, as will be explained, the switch portion 22shown in FIG. .2 is brazed in a hydrogen oven. Hydrogen is, thus, sealedinside the switch portionj This hydrogen must be removed to create ahigh vacuum. The hydrogen left inside may, in fact, be removed bydiffusing it through portion 44 at an elevated temperature. This is truebecause nickel and nickel-iron may be penetrated by hydrogen gas atelevated temperatures.

A relatively thin metallic diaphragm 46 is hermetically brazed to thelower metallized edge 34 of the ceramic section 28. A third terminalelectrode 48 is interposedbetween the upper metallized edge 36 of theceramic section 30 and the lower surface of the metallic diaphragm 46.This electrode provides a terminal for the actuator rod 50.

The diaphragm 46 is sufficiently flexible to permit transverse pivotalmovement of the longitudinally extending actuator rod. The rod isprovided with a lower ceramic contact end 50 extending toward theactuating assembly 24, while the upper end 54 of the actuator rodextends through a central aperture formed in the flexible diaphragm 46and is hermetically brazed thereto. The upper surface of the ceramiccontact end 52 is metallized as indicated at 55 and brazed to thediaphragm 46. The terminal electrodes 38, 40 and 48 are preferablyformed of copper to provide a high currentcarrying capacity while theactuator rod 50 is formed of a metal which is substantially harder thanthe terminal electrodes so that it willnot bend from impact with theterminal electrodes.

The terminal electrodes 38 and 40 are conveniently formed from sheetcopper stamped into the configuration desired. As shown, the preferredconfiguration is one in which the portions of the terminal electrodes 38and 40 within the ceramic envelope are dished toward each other asindicated at 60 are provided on the terminal electrodes. Rods'60 havesubstantially the same hardness as the actuator rod and, hence,substantially greater hardness than that of the terminal electrodes.Preferably, the actuator rod and contact rods are *formed of refractorymetals, such as titanium, tungsten, or

molybdenum or of base metals such as iron, chromium, nickel, or alloysthereof. These materials are substantially harder than the copperterminal electrodes. Also, it is preferable that the actuator rod befonned of a metal different than the metal of the contact rods so thatwelding of the rods will not occur upon continued impact therebetween.

One of the wires 60 is pressed into aligned grooves 62 and 64 in thelower surface of the dished portion 56 of electrode 38. The other wire60 is pressed into aligned grooves 66 and 68 in'the top surface of thedished portion of the electrode '40.

The pairs of grooves in each of the electrodes 38 and 40 are preferablyaligned and so arranged that the wire contacts 60 are parallel to eachother and form cords across the circular openings 58 inthe electrodes.Preferably, the rods 60 are disposed so that the movement of the pivotedactuator rod is normal to the contact rods to insure firm contacttherebetween.

The wires 60 may be mounted on the dished portions of electrodes 38 and40 by forming the grooves initially in the electrodes and forcing thewires therein. Alternatively, a die having appropriately arrangedgrooves may be placed in the dished portion of the electrodes so thatupon pressing the wire contacts against the opposite side of theelectrodes toward the .die grooves, grooves will be formed in theelectrodes simultaneously with securing the wires therein. With eithermethod, the contact rods can be accurately located in any predeterminedposition depending upon the spacial relationship desired between therods. Also, the rods can be positioned in exact parallel relationship sothat there is a uniform gap between the two fixed contact surfaces. Ifdesired, after the contact rods are pressed into the terminalelectrodes, they may be brazed at the point of contact with theelectrodes although this is not essential.

It can be appreciated that substantial latitude is available at the timeof assembly as to the material of the fixed contacts which will beprovided in the relay, i.e., contact rods fomied of any one of themetals mentioned herein may be utilized and without requiring the use ofentire terminal electrodes of different materials.

During the manufacture of relays, depending upon how the method of theinvention is used, it is sometimes possible by the prior method that anoxidation film will form or'rthe contact rods, thus increasing thecontact resistance of the relays. Thus, if desired, a coating of metalmay be provided on the rods. The coating may have a higher electricaland thermal conductivity than that of the rods per se. Examples ofmetals for the coating are copper and noble metals, such as gold andsilver, which are applied to the contact rods prior to assembly thereofto the terminal electrodes. The coating may be applied byelectrodeposition, vapor deposition, or sputtering techniques. Thecoating may have a thickness of only a few atoms to about 0.005 inch tomaintain the contact resistance of the relay at a minimum, yetstill'take full advantage of the hardness of the base contact rodmaterial to minimize deformation of the contact rods when contacted bythe actuator rod. Even though the coating is itself subject todeformation when contacted by the actuator rod, since the coating isquite thin, such deformation is only slight. Moreover, since the coatingmaterial is highly malleable, it tends to flow and, therefore, fill upany deformed surface area. This invention removes the requirement forcoating the rods, thereby reducing the number of operations required toproduce a low contact resistance relay.

Summarizing, straight wire "contacts 60 are rigid and parallel. Theyalso are formed of a material having substantially the same hardness asthat of the actuator rod 54 so that upon contact of the actuator rodwith the contact rods, a minimum amount of deformation of the materialsresults with a resultant minimum degree of variation in the electricalcharacteristics of the relay over extended use of the relay.Furthennore, since the metal wires 60, present fixed, straight,generally parallel, opposed contact surfaces, there will be no variationin the electrical characteristics of the relay even if the path ofmovement of the actuator rod varies in a direction parallel to suchrods. Also, because the wire contacts 60 are mounted on the dishedportions of the electrodes 38 and 40, the contacts are spaced axiallyapart in a relatively short distance, thus minimizing the amount ofpivotal movement required for the actuator rod 50 to engage the contactwires. ln addition, the dished portions 56 of the electrodes 38 and 40serve as shields to obstruct any vaporized metal which might be producedby the actuator rod 54 striking the contact wires 60 from impinging uponthe inner surfaces of the ceramic sections 26 and 28. Finally, theelectrodes 38 and 40 are of identical form, except for the location ofthe contacts 60, thus reducing the number of different parts required inthe manufacture of the relay. The small rods 60 are easily manufacturedby merely cutting proper lengths of wire.

Reference is now made to FIGS. 5 through 10 which show in detailthe-construction of the actuating assembly 24 for the actuating rod 50.The assembly 24 includes a tubular metallic casing which is coaxial withthe tubular switch portion 22 of the relay and is brazed at its upperend to the metallized portion 37 of ceramic section 30. A housing 70,within which is supported an electromagnetic coil 74, is positioned atthe lower portion of the casing 70 andv retained therein by a disc 75.Terminals 76 and 78 extending through the disc are provided forconnecting the coil to a source of electrical power. The coil surroundsa core 80 which is coaxial with the longitudinal axis of the tubularcasing 70 and extends upwardly through the upper end 82 of the housing72.

An armature 84 is positioned above the housing 72 and extends across theupper end 86 of the core. A resilient bracket, generally designated 88,pivotally mounts the armature'84 within the casing 70 and biases thearmature upwardly, that is, in a direction opposite to the force appliedby the coil 74 when energized.

The bracket 88 is formed from a sheet metal blank 90 having theconfiguration shown in FIG. 8. The blank 90 has a circular end 92 inwhich a circular cutout 94 is provided. The other end of the blank 90 isprovided with an outwardly flared tab 96. lntennediate the two ends ofthe blank is an opening 98.

The housing 72 is bent inwardly at the upper end to provide an annularflange 100. The blank 90 is bent into the configuration shown in FIGS. 5and 6 with an upwardly bent portion 102 of the circular end 92 extendingover the upper surface of one end of the armature 84 retaining the samein relatively fixed position, yet with sufficient spacing being providedbetween the two parts to permit upward pivotal movement of the armature84 in the casing 70. The portions 104 of the circular end 92 of thebracket on opposite sides of the upwardly extending section 102 aresecured by means of brazing or welding to the flange 100. 4

The outwardly flared tab 96 on the opposite end. of the bracket 88 isfitted into a complementary shaped slot 106 at the end of the armature84 opposite that which is engaged under the circular end 92 of thebracket, as best seen in FIG. 9, thereby providing a fixed connectionbetween the free end of the armature and the bracket.

The bracket is bent upwardly to provide generally vertical legs 108 and110 which meet at an upper end 112 in which the opening 98 is provided.The lower end 52 of the actuator rod 50 is slidably positioned in theopening 98, thereby providing a lost mo tion connection between theactuator rod and the bracket 98.

The resilient pressure asserted by the bracket 88 retains the armature84 in the position illustrated in FIG. .5 wherein the armature is spacedfrom the end 86 of core 80. Upon energization of the coil 74, themagnetic field generated thereby attracts the mature down against theresilient force asserted by the bracket 88 so that the end 86 of thecore 80 is abutted by the armature. During the downward movement of theamiature, the upper portion 112 of the bracket 88 will shift in therightward direction as viewed in FIG. 5, thereby pivoting the actuatorrod about its fulcrum provided by the diaphragm 46.

As can best be seen, the actuating assembly 24 is of extremely simpleconstruction, requiring only a single metal element, namely theresilient bracket 88, for both pivotally mounting the armature 84 andfor providing a lost-motion connection with the actuator rod 50 forshifting the latter.

According to the method of the present invention, only the switchportion 22 of the relay shown in FIG. 2 need be processed as follows.Actuating assembly 24 need not be so processed.

According to the method of the invention, all the I component parts ofswitch portion 22 shown in FIG. 2 may be stacked or jigged or bothbefore they are hennetically sealed together. Certain components may befixed together before the final sealing step, if desired. Final sealingmay be accomplished by brazing the parts to be brazed in a conventionaloven containing hydrogen gas. The gas, thus, surrounds the assembledparts of switch portion 22 and also fills the space inside switchportion 22 along its entire axial length. Thepressure of the hydrogen is1 atmosphere. There is, thus, no need for a vacuum pump at this pointand brazing may be done easily and quickly simply by raising the oventemperature to a conventional brazing temperature for a conventionalbrazing compound.

Preferably, the hydrogen oven has a dewpoint of less than 70 F. Thehydrogen oven preferably should be as dry as possible and at leastsufliciently dry to prevent an unwanted amount of water vapor frombeingirretrievably sealed off inside the switch portion 22. Water vaporsealed inside the switch portion 22 generally will not penetrate end cap42, at least within a reasonable time at practical temperatures andpressures. Due to the fact that brazing is performed according to themethod of the present invention at an elevated temperature employed forend cap 42 when hydrogen is used.

Hydrogen has the most rapid diffusion rate (increasing production)through palladium. Palladium may also be used for end cap 42 or for asmaller window, if desired. With hydrogen, end cap 42 may also be madeof nickel-copper or pure iron. Nickel-iron, nickel-copper, and pure ironhave hydrogen diffusion rates of the same order of magnitude, i.e., fromID to 100 percent that of nickel. Nickel has about the hi est hydrogendiffusionrate, except for palladium.

e carbon monoxide diffusion ra e through iron lS about 1 percent of thediffusion rate of hydrogen through nickel.

The invention is, thus, not limited to the use of hydrogen. Further, theinvention is not limited to the use of any specific brazing orevacuation times or temperatures or pressures. Further, the invention isnot limited to any particular pressure inside switch portion 22.

The invention is also not limited to the use of one particular set ofmaterials.

in accordance with the foregoing, it will be appreciated that it is anoutstanding advantage of the method of the present invention that alarge number of switch portions identical to switch portion 22 may becleanly brazed simultaneously. The

' same large number may also be evacuated simultaneously. A

and at atmospheric pressure, the hydrogen in the interior of switchportion 22 will be below atmospheric pressure if it is allowed to coolto room temperature. The pressure may drop to, for example, one-third of1 atmosphere.

After the brazing step has been performed, the hydrogenfilled switchportion 22 is preferably placed in a conventional vacuum oven and heatedto 700 C. for minutes. The pressure around the outside of switch portion22 at the same time may, for example, be reduced to 10" Torr although itis preferably reduced. to between about 10" Torr and 10" Torr for about45 minutes. The time during evacuation is, by no means, critical and maybe more or less than 45 minutes depending upon to what pressure it isdesirable to evacuate switch portion 22 and what temperature isemployed.

After evacuation, switch portion 22 may be cooled to room temperature.It isthen ready for use.

Hydrogen gas need not necessarily be employed during brazing, althoughhydrogen is preferred. For example, carbon monoxide may be employed.However, end cap 42 is preferably made of iron if carbon monoxide isemployed.

Nickel-iron in proportions of 1:1 by weight is preferably substantialincrease in production may, thus, be achieved without a correspondingincrease in cost.

We claim:

l. The method of making an evacuated enclosure, said method comprisingthe steps of: hermeticallysealing an envelope with a gas inside thereof,said envelope having at least one portion through which said gas willdiffuse; and reducing the pressure of gas around the outside of saidenvelope at least at said portion to a pressure sufficiently below thatinside said envelope to cause said gas inside said envelope to diffusethrough said envelope portion.

2. The invention as defined in claim 1, wherein said envelope includesat least two component parts, said sealing step including brazing saidparts together in an atmosphere of hydrogen gas at a brazingtemperature, the gas left inside said envelope thereby being hydrogen,said brazing step being performed in a hydrogen oven with a dewpoint ofless than 70 F., placing said envelope in a vacuum oven, increasing saidvacuum oven temperature to about 700 C. for about 45 minutes, reducingthe pressure in said vacuum oven to between about 10' to 10" Torr duringsaid 45 minutes.

3. The invention as defined in claim 2, wherein said envelope portion ismade of nickel.

4. The invention as defined in claim 2, wherein said envelope portion ismade of two uniformly mixed metals, said metals being nickel and iron.

5. The invention as defined in claim 1, wherein said envelope ishermetically sealed at atmospheric pressure in a reducing atmosphere ata temperature above room temperature, said method including the step ofheating said sealed envelope and the gas therein at the same time thepressure of the gas therearound is reduced.

6. The invention as defined in, claim 1, wherein, said envelope ishermetically sealed in a reducing atmosphere.

7. The invention as defined in claim I, wherein said envelope is sealedat atmospheric pressure.

8. The invention as defined in claim 1, wherein said sealing step isperformed at a temperature above room temperature.

9. The invention as defined in claim 1, wherein said method includes thestep of heating said sealed envelope and the gas therein at the sametime the pressure of the gas therearound is reduced.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3, 576,066 DatedApril 27 1971 Lewis B. Steward et a1 Patent No.

Inventor(s) It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 5 line 54, "10 should read 10' line "10 and "10 should read 10'and 10' respectively. Column 6, line 44 "10 and "10 should read 10' and10' respectively.

Signed and sealed this 31st day of August 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, Attesting OfficerCommissioner of Pate FORM FWD-1050 (10-69) USCOMM 0c 5037

1. The method of making an evacuated enclosure, said method comprisingthe steps of: hermetically sealing an envelope with a gas insidethereof, said envelope having at least one portion through which saidgas will diffuse; and reducing the pressure of gas around the outside ofsaid envelope at least at said portion to a pressure sufficiently belowthat inside said envelope to cause said gas inside said envelope todiffuse through said envelope portion.
 2. The invention as defined inclaim 1, wherein said envelope includes at least two component parts,said sealing step including brazing said parts together in an atmosphereof hydrogen gas at a brazing temperature, the gas left inside saidenvelope thereby being hydrogen, said brazing step being performed in ahydrogen oven with a dewpoint of less than -70* F., placing saidenvelope in a vacuum oven, increasing said vacuum oven temperature toabout 700* C. for about 45 minutes, reducing the pressure in said vacuumoven to between about 10 6 to 10 8 Torr during said 45 minutes.
 3. Theinvention as defined in claim 2, wherein said envelope portion is madeof nickel.
 4. The invention as defined in claim 2, wherein said envelopeportion is made of two uniformly mixed metals, said metals being nickeland iron.
 5. The invention as defIned in claim 1, wherein said envelopeis hermetically sealed at atmospheric pressure in a reducing atmosphereat a temperature above room temperature, said method including the stepof heating said sealed envelope and the gas therein at the same time thepressure of the gas therearound is reduced.
 6. The invention as definedin claim 1, wherein said envelope is hermetically sealed in a reducingatmosphere.
 7. The invention as defined in claim 1, wherein saidenvelope is sealed at atmospheric pressure.
 8. The invention as definedin claim 1, wherein said sealing step is performed at a temperatureabove room temperature.
 9. The invention as defined in claim 1, whereinsaid method includes the step of heating said sealed envelope and thegas therein at the same time the pressure of the gas therearound isreduced.